Method and apparatus for installing geothermal heat exchanger

Abstract

A borehole is bored to a borehole target depth in a site and a geothermal heat exchanger is inserted into and then secured in the borehole at the desired depth. Once the heat exchanger has been secured in the borehole, the heat exchanger has a closed distal end and an open proximal end and has at least one fluid path between the closed distal end and the open proximal end, with installation fluid disposed in the fluid path(s). After securing the heat exchanger in the borehole and before excavation of a portion of the site immediately surrounding the borehole, the heat exchanger is temporarily sealed by installing, through the open proximal end, at least one respective internal seal in each fluid path. For each fluid path, the internal seal(s) will be disposed below a respective notional subgrade depth and excavation of the site immediately surrounding the borehole can proceed.

What is claimed is: 
     
       1. A method of installing a geothermal heat exchanger, the method comprising:
 at a site, boring a borehole to a borehole target depth in the site; 
 after boring the borehole, inserting a geothermal heat exchanger into the borehole to a desired heat exchanger depth, 
 after inserting the heat exchanger into the borehole, securing the heat exchanger in the borehole at the desired heat exchanger depth; 
 wherein, when the heat exchanger has been secured in the borehole:
 the heat exchanger has a closed distal end and an open proximal end; 
 the heat exchanger has at least one fluid path between the closed distal end and the open proximal end; and 
 installation fluid is disposed in each of the at least one fluid path of the heat exchanger; and 
 
 after securing the heat exchanger in the borehole and before excavation of a portion of the site immediately surrounding the borehole, and without withdrawing the heat exchanger from the borehole, temporarily sealing the heat exchanger between the closed distal end and the open proximal end by installing, through the open proximal end, at least one respective internal seal in each of the at least one fluid path, wherein for each of the at least one fluid path, the at least one internal seal is disposed below a respective notional subgrade depth; 
 after temporarily sealing the heat exchanger, cutting the heat exchanger above an uppermost one of the at least one seal to produce at least one above-seal cut portion of the heat exchanger; 
 after cutting the heat exchanger, removing each above-seal cut portion of the heat exchanger and excavating the portion of the site immediately surrounding the borehole; 
 wherein excavating the portion of the site immediately surrounding the borehole is above a lowermost of the notional subgrade depth; and 
 after excavating the portion of the site immediately surrounding the borehole, removing the seals for connection of the heat exchanger to supply/return conduits. 
 
     
     
       2. The method of  claim 1 , wherein cutting the heat exchanger and removing each above-seal cut portion of the heat exchanger is carried out before excavation of the site. 
     
     
       3. The method of  claim 1 , wherein cutting the heat exchanger is carried out by inserting a pipe cutting tool into the open proximal end and cutting the heat exchanger from the inside. 
     
     
       4. The method of  claim 1 , wherein cutting the heat exchanger and removing each above-seal cut portion of the heat exchanger is carried out during excavation of the site. 
     
     
       5. The method of  claim 4 , wherein cutting is performed by use of a pipe cutting tool. 
     
     
       6. The method of  claim 4 , wherein cutting is performed by excavating machinery during excavation of the portion of the site immediately surrounding the borehole. 
     
     
       7. The method of  claim 1 , further comprising:
 after securing the heat exchanger in the borehole and before excavation of the site, testing the heat exchanger. 
 
     
     
       8. The method of  claim 1 , wherein the installation fluid remains in the heat exchanger during securing of the heat exchanger in the borehole and temporarily sealing the heat exchanger. 
     
     
       9. The method of  claim 1 , wherein the heat exchanger is a U-loop. 
     
     
       10. The method of  claim 9 , wherein the heat exchanger is a single U-loop. 
     
     
       11. The method of  claim 9 , wherein the heat exchanger is a multiple U-loop. 
     
     
       12. The method of  claim 1 , wherein the heat exchanger is at least an outer tube of a concentric heat exchanger.